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Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy characterized by the clonal expansion of myeloid blasts in the peripheral blood, bone marrow, and/or other tissues. It is the most common form of acute leukemia among adults and accounts for the largest number of annual deaths from leukemias in the United States. Like AML, blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a myeloid malignancy. It is a rare malignancy characterized by the aggressive proliferation of precursors of plasmacytoid dendritic cells that frequently involves the bone marrow, skin, central nervous system, and other organs and tissues. This discussion section focuses on the diagnosis and management of BPDCN as outlined in the NCCN Guidelines for AML.

Nelarabine, an antimetabolite prodrug, is approved as monotherapy for children and adults with relapsed and refractory T-cell acute lymphoblastic leukemia and lymphoma (R/R T-ALL/LBL), although it is often used in combination regimens. We sought to understand differences in efficacy and toxicity when nelarabine is administered alone or in combination. We retrospectively analyzed 44 consecutive patients with R/R T-ALL/LBL; 29 of whom were treated with combination therapy, most with cyclophosphamide and etoposide (23, 79%) and 15 with monotherapy. The median age was 19 years (range, 2-69), including 18 children (

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy with historically poor outcomes and no worldwide consensus treatment approach. Unique among most hematologic malignancies for its frequent cutaneous involvement, BPDCN can also invade other extramedullary compartments, including the central nervous system. Generally affecting older adults, many patients are unfit to receive intensive chemotherapy, and although hematopoietic stem cell transplantation is preferred for younger, fit individuals, not all are eligible. One recent therapeutic breakthrough is that all BPDCNs express CD123 (IL3Rα) and that this accessible surface marker can be pharmacologically targeted. The first-in-class agent for BPDCN, tagraxofusp, which targets CD123, was approved in December 2018 in the United States for patients with BPDCN aged ≥2 years. Despite favorable response rates in the frontline setting, many patients still relapse in the setting of monotherapy, and outcomes in patients with relapsed/refractory BPDCN remain dismal. Therefore, novel approaches targeting both CD123 and other targets are actively being investigated. To begin to formally address the state of the field, we formed a new collaborative initiative, the North American BPDCN Consortium (NABC). This group of experts, which includes a multidisciplinary panel of hematologists/oncologists, hematopoietic stem cell transplant physicians, pathologists, dermatologists, and pediatric oncologists, was tasked with defining the current standard of care in the field and identifying the most important research questions and future directions in BPDCN. The position findings of the NABC’s inaugural meetings are presented herein.

Asparaginase is a key component of pediatric-inspired regimens in young adults with acute lymphoblastic leukemia (ALL). Truncation of asparaginase therapy is linked to inferior outcomes in children with ALL. However, a similar correlation in adults is lacking. Here, we studied the prevalence and risk factors associated with pegylated (PEG)-asparaginase discontinuation in young adults with ALL treated on the US intergroup Cancer and Leukemia Group B (CALGB) 10403 study and examined the prognostic impact of early discontinuation (ED) (defined as

Both an improved understanding of acute myeloid leukemia (AML) pathophysiology plus improvements in measurement technology have led to revamping the diagnostic, prognostic, and therapeutic landscape of AML. New classification systems integrating molecular insights, updated risk assessment, improved ability to measure low levels of disease as well as least ten recently approved therapies may promote better outcomes including cures in a larger fraction of AML patients. The diagnostic and therapeutic complexity makes the decision-making process ever more individualized and requires integration of patient goals of care, comorbidities and disease characteristics including the specific mutational profile of the patient. In this review we present recent advances in diagnosis, classification, risk stratification and treatment options for patients with newly diagnosed (ND) or relapsed and refractory (R/R) AML. Such advances are welcome, but the increased options also lead to many controversies concerning the optimal selection of the timing and combinatorial use of the new drugs and how best to leverage our burgeoning ability to measure a small number of potentially malignant myeloid cells. In this context, we will present our approach for AML management noting current limitations and potential future directions. This article is protected by copyright. All rights reserved.

Purpose:Patients with relapsed/refractory (R/R) acute myeloid leukemia (AML) have poor outcomes and require new therapies. In AML, autocrine production of hepatocyte growth factor (HGF) drives MET signaling that promotes myeloblast growth and survival, making MET an attractive therapeutic target. MET inhibition exhibits activity in AML preclinical studies, but HGF upregulation by the FGFR pathway is a common mechanism of resistance.Patients and Methods:We performed preclinical studies followed by a Phase I trial to investigate the safety and biological activity of the MET inhibitor merestinib in combination with the FGFR inhibitor LY2874455 for patients with R/R AML. Study Cohort 1 underwent a safety lead-in to determine a tolerable dose of single-agent merestinib. In Cohort 2, dose-escalation of merestinib and LY2874455 was performed following a 3+3 design. Correlative studies were conducted.Results:The primary dose-limiting toxicity (DLT) observed for merestinib alone or with LY2874455 was reversible grade 3 transaminase elevation, occurring in 2 of 16 patients. Eight patients had stable disease and one achieved complete remission (CR) without measurable residual disease. Although the MTD of combination therapy could not be determined due to drug supply discontinuation, single-agent merestinib administered at 80 mg daily was safe and biologically active. Correlative studies showed therapeutic plasma levels of merestinib, on-target attenuation of MET signaling in leukemic blood, and increased HGF expression in bone marrow aspirate samples of refractory disease.Conclusions:We provide prospective, preliminary evidence that MET and FGFR are biologically active and safely targetable pathways in AML.

PURPOSE Representativeness in acute leukemia clinical research is essential for achieving health equity. The National Cancer Institute's mandate for Comprehensive Cancer Centers (CCCs) to define and assume responsibility for cancer control and treatment across a geographic catchment area provides an enforceable mechanism to target and potentially remediate participatory inequities. METHODS We examined enrollee characteristics across 15 Cancer and Leukemia Group B/Alliance cooperative group adult acute leukemia clinical trials (N = 3,734) from 1998 to 2013, including participation in optional companion biobanks. We determined enrollment odds by race-ethnicity for all participants adjusted for national incidence, and for those enrolled at CCCs adjusted for catchment area incidence. We modeled biobank participation by sociodemographics using logistic regression. RESULTS Non-Hispanic (NH)-White patients were more likely to be enrolled than NH-Black, NH-Asian, or Hispanic patients (odds ratio [OR], 0.75, 0.48, and 0.44, respectively; all P < .001), but less likely than NH-Native American patients (OR, 1.91; P < .001), adjusted for national incidence. Enrollment odds were lower for NH-Black, NH-Asian, and Hispanic patients at CCCs adjusted for catchment area incidence (OR, 0.57, 0.26, and 0.32, respectively; P < .001); differences were driven by overenrollment of NH-White patients from outside self-defined catchment areas (18.1% v 12.3%; χ2 P = .01) and by CCCs with less absolute enrollee diversity (rank sum P = .03). Among all enrollees, NH-White race-ethnicity and lower neighborhood deprivation correlated with biobank participation (OR, 1.81 and 1.45, respectively; P = .01 and .03). For CCC enrollees, the correlation of race-ethnicity with biobank participation was attenuated by a measure accounting for their site's degree of enrollment disparity but not neighborhood deprivation. CONCLUSION Acute leukemia clinical research disparities are substantial and driven by structural trial enrollment barriers at CCCs. Real-time CCC access and enrollment monitoring is needed to better align research participation with local populations.

FLT3, IDH1 and IDH2 inhibitors as well as venetoclax in combination with hypomethylating agents or low-dose cytarabine have expanded treatment options for patients with acute myeloid leukemia (AML). However, little data exist on the efficacy of venetoclax-based therapies in AML patients previously treated with FLT3 or IDH1/2 inhibitors. In this multicenter, retrospective cohort study, we included 44 patients who received venetoclax-based therapy after FLT3, IDH1 or IDH2 inhibitors. The overall response rate (ORR; composite of complete remission [CR]/CR with incomplete count recovery, partial remission, and morphologic leukemia free state) was 56.8% (18.2% CR) and a median overall survival of 9.2 months. While 6 out of 7 patients with

Menin interacts with oncogenic MLL1-fusion proteins, and small molecules that disrupt these associations are in clinical trials for leukemia treatment. By integrating chromatin-focused and genome-wide CRISPR screens with genetic, pharmacologic, and biochemical approaches, we discovered a conserved molecular switch between the MLL1–Menin and MLL3/4–UTX chromatin-modifying complexes that dictates response to Menin–MLL inhibitors. MLL1–Menin safeguards leukemia survival by impeding the binding of the MLL3/4–UTX complex at a subset of target gene promoters. Disrupting the Menin–MLL1 interaction triggers UTX-dependent transcriptional activation of a tumor-suppressive program that dictates therapeutic responses in murine and human leukemia. Therapeutic reactivation of this program using CDK4/6 inhibitors mitigates treatment resistance in leukemia cells that are insensitive to Menin inhibitors. These findings shed light on novel functions of evolutionarily conserved epigenetic mediators like MLL1–Menin and MLL3/4–UTX and are relevant to understand and target molecular pathways determining therapeutic responses in ongoing clinical trials. Significance: Menin–MLL inhibitors silence a canonical HOX- and MEIS1-dependent oncogenic gene expression program in leukemia. We discovered a parallel, noncanonical transcriptional program involving tumor suppressor genes that are repressed in Menin–MLL inhibitor–resistant leukemia cells but that can be reactivated upon combinatorial treatment with CDK4/6 inhibitors to augment therapy responses. This article is highlighted in the In This Issue feature, p. 1

Survival of patients with acute myeloid leukemia (AML) is inversely associated with age, but the impact of race on outcomes of adolescent and young adult (AYA; range, 18-39 years) patients is unknown. We compared survival of 89 non-Hispanic Black and 566 non-Hispanic White AYA patients with AML treated on frontline Cancer and Leukemia Group B/Alliance for Clinical Trials in Oncology protocols. Samples of 327 patients (50 Black and 277 White) were analyzed via targeted sequencing. Integrated genomic profiling was performed on select longitudinal samples. Black patients had worse outcomes, especially those aged 18 to 29 years, who had a higher early death rate (16% vs 3%; P=.002), lower complete remission rate (66% vs 83%; P=.01), and decreased overall survival (OS; 5-year rates: 22% vs 51%; P

Antifungal prophylaxis (AFP) is recommended for acute myeloid leukemia (AML) patients receiving the combination of venetoclax (VEN) and a hypomethylating agent (HMA), but the benefit of this practice is unclear. We identified 131 patients with newly diagnosed AML who received frontline VEN/HMA and evaluated the use of AFP and its association with invasive fungal infections (IFIs) and AML outcomes. Seventeen percent of our patients received AFP at any time. Overall incidence of any IFI ('possible,' 'probable,' or 'proven' infection, as defined by the European Mycoses Study Group) was 13%, and the incidence did not differ based on AFP use (

The aim of this study was to characterize the mutational landscape of patients with FLT3-mutated acute myeloid leukemia (AML) treated within the randomized CALGB 10603/RATIFY trial evaluating intensive chemotherapy plus the multi-kinase inhibitor midostaurin versus placebo. We performed sequencing of 262 genes in 475 patients: mutations occurring concurrently with the FLT3-mutation were most frequent in NPM1 (61%), DNMT3A (39%), WT1 (21%), TET2 (12%), NRAS (11%), RUNX1 (11%), PTPN11 (10%), and ASXL1 (8%) genes. To assess effects of clinical and genetic features and their possible interactions, we fitted random survival forests and interpreted the resulting variable importance. Highest prognostic impact was found for WT1 and NPM1 mutations, followed by white blood cell count, FLT3 mutation type (internal tandem duplications vs. tyrosine kinase domain mutations), treatment (midostaurin vs. placebo), ASXL1 mutation, and ECOG performance status. When evaluating two-fold variable combinations the most striking effects were found for WT1:NPM1 (with NPM1 mutation abrogating the negative effect of WT1 mutation), and for WT1:treatment (with midostaurin exerting a beneficial effect in WT1-mutated AML). This targeted gene sequencing study provides important, novel insights into the genomic background of FLT3-mutated AML including the prognostic impact of co-mutations, specific gene–gene interactions, and possible treatment effects of midostaurin.

Frontline arsenic trioxide (ATO)–based treatment regimens achieve high rates of long-term relapse-free survival in treating acute promyelocytic leukemia (APL) and form the current standard of care. Refining prognostic estimates for newly diagnosed patients treated with ATO-containing regimens remains important in continuing to improve outcomes and identify patients who achieve suboptimal outcomes. We performed a pooled analysis of exclusively ATO-treated patients at a single academic institution and from the ALLG APML4 and Alliance C9710 studies to determine the prognostic importance of additional cytogenetic abnormalities and/or complex karyotype. We demonstrated inferior event-free survival for patients harboring complex karyotype (hazard ratio [HR], 3.74; 95% confidence interval [CI], 1.63-8.56; P = .002), but not for patients harboring additional cytogenetic abnormalities (HR, 2.13; 95% CI, 0.78-5.82; P = .142). These data support a role for full karyotypic analysis of all patients with APL and indicate a need for novel treatment strategies to overcome the adverse effect of APL harboring complex karyotype.

PURPOSE Chemotherapy outcomes in older patients with Philadelphia (Ph) chromosome–negative B-acute lymphoblastic leukemia (ALL) are very poor. Here, we evaluated blinatumomab as induction and consolidation therapy followed by prednisone, vincristine, 6-mercaptopurine, and methotrexate (POMP) maintenance chemotherapy in this patient population. PATIENTS AND METHODS Patients were treated at National Clinical Trial Network sites. Eligibility criteria included age ≥ 65 years and newly diagnosed Ph chromosome–negative B-ALL. Patients received blinatumomab as induction for one-two cycles until attainment of response (complete remission (CR) and CR with incomplete count recovery). Patients then received three cycles of consolidation with blinatumomab followed by 18 months of POMP maintenance chemotherapy. Eight doses of intrathecal methotrexate were administered as central nervous system prophylaxis. RESULTS Twenty-nine eligible patients were enrolled. The median age was 75 years, and the median bone marrow blast count at diagnosis was 87%. Cytogenetic risk was poor in 10 patients (34%), and five of 14 patients (36%) tested had the Ph-like ALL gene signature. Nineteen patients (66%; 95% CI, 46 to 82) achieved CR. Kaplan-Meier 3-year disease-free survival and overall survival estimates were 37% (95% CI, 17 to 57) and 37% (95% CI, 20 to 55), respectively. CONCLUSION Blinatumomab was well tolerated and effective in the treatment of older patients with newly diagnosed Ph chromosome–negative B-ALL, including patients with poor-risk cytogenetics. The 3-year disease-free survival and overall survival results are encouraging and suggest that this approach should be further explored.

Polycomb repressive epigenetic complexes are recurrently dysregulated in cancer. Unlike polycomb repressive complex 2 (PRC2), the role of PRC1 in oncogenesis and therapy resistance is not well-defined. Here, we demonstrate that highly recurrent mutations of the PRC1 subunits BCOR and BCORL1 in leukemia disrupt assembly of a noncanonical PRC1.1 complex, thereby selectively unlinking the RING-PCGF enzymatic core from the chromatin-targeting auxiliary subcomplex. As a result, BCOR-mutated PRC1.1 is localized to chromatin but lacks repressive activity, leading to epigenetic reprogramming and transcriptional activation at target loci. We define a set of functional targets that drive aberrant oncogenic signaling programs in PRC1.1-mutated cells and primary patient samples. Activation of these PRC1.1 targets in BCOR-mutated cells confers acquired resistance to treatment while sensitizing to targeted kinase inhibition. Our study thus reveals a novel epigenetic mechanism that explains PRC1.1 tumor-suppressive activity and identifies a therapeutic strategy in PRC1.1-mutated cancer. Significance: We demonstrate that BCOR and BCORL1 mutations in leukemia unlink PRC1.1 repressive function from target genes, resulting in epigenetic reprogramming and activation of aberrant cell signaling programs that mediate treatment resistance. Our study provides mechanistic insights into the pathogenesis of PRC1.1-mutated leukemia that inform novel therapeutic approaches. This article is highlighted in the In This Issue feature, p. 85

The JAK2-V617F mutation is the most common cause of myeloproliferative neoplasms. While experiments have shown that this gain-of-function mutation is associated with myeloid blood cell expansion and increased production of white cells, red cells and platelets, the transcriptional consequences of the JAK2-V617F mutation in different cellular compartments of the bone marrow have not yet been fully elucidated. To study the direct effects of JAK2-V617F on bone marrow cells in myeloproliferative neoplasm patients, we performed joint single-cell RNA sequencing and JAK2 genotyping on CD34+ enriched cells from 8 patients with newly diagnosed essential thrombocythemia or polycythemia vera. We found that the JAK2-V617F mutation increases the expression of interferon-response genes (e.g., HLAs) and the leptin receptor in hematopoietic progenitor cells. Furthermore, we sequenced a population of CD34-bone marrow monocytes and found the JAK2 mutation increased expression of intermediate monocyte genes and the fibrocyte-associated surface protein SLAMF7 in these cells.

Survival of patients with acute myeloid leukemia (AML) is influenced by genetic factors, age, and race. Social deprivation is increasingly recognized as an important contributor to disparities in cancer outcomes, but studies of adult AML are lacking. We analyzed associations between social deprivation index (SDI) and outcome in 1,893 patients with AML treated on Cancer and Leukemia Group B/Alliance for Clinical Trials in Oncology frontline protocols. Patients with low (first quartile, lowest deprivation) and high (quartiles 2-4) SDI were analyzed for associations with baseline clinical, cytogenetic and molecular features, and outcomes. Except for racial-ethnic identity, SDI was not associated with baseline clinical characteristics. Patients aged

PURPOSE Clinical trials are important for managing older patients with AML. We investigated differences in outcomes of older patients with AML on the basis of whether patients participated in intensive chemotherapy trials at community versus academic cancer centers. METHODS We used data from the Alliance for Clinical Trials in Oncology phase III trials that enrolled patients age ≥ 60 years with newly diagnosed AML between 1998 and 2002 in the Cancer and Leukemia Group B (CALGB) 9720 trial and between 2004 and 2006 in the CALGB 10201 trial. Centers funded by the NCI Community Oncology Research Program were identified as community cancer centers; others were designated as academic cancer centers. Logistic regression models and Cox proportional hazards models were used to compare 1-month mortality and overall survival (OS) by center type. RESULTS Seventeen percent of the 1,170 patients were enrolled in clinical trials in community cancer centers. The study results demonstrated comparable rates of grade ≥3 adverse events (97% v 93%), 1-month mortality (19.1% v 16.1%), and OS (43.9% v 35.7% at 1 year) between community versus academic cancer centers, respectively. After adjusting for covariates, 1-month mortality (odds ratio, 1.40; 95% CI, 0.92 to 2.12; P = .11) and OS (hazard ratio, 1.04; 95% CI, 0.88 to 1.22; P = .67) were not statistically different among patients treated in community versus academic cancer centers. CONCLUSION An older patient population, who have complex health care needs, can be successfully treated on intensive chemotherapy trials in select community cancer centers with outcomes comparable with that achieved at academic cancer centers.

Supplementary Figure from The Impact of Inflammation-Induced Tumor Plasticity during Myeloid Transformation

ChIP-Seq results

Polycomb repressive epigenetic complexes are recurrently dysregulated in cancer. Unlike polycomb repressive complex 2 (PRC2), the role of PRC1 in oncogenesis and therapy resistance is not well-defined. Here, we demonstrate that highly recurrent mutations of the PRC1 subunits BCOR and BCORL1 in leukemia disrupt assembly of a noncanonical PRC1.1 complex, thereby selectively unlinking the RING-PCGF enzymatic core from the chromatin-targeting auxiliary subcomplex. As a result, BCOR-mutated PRC1.1 is localized to chromatin but lacks repressive activity, leading to epigenetic reprogramming and transcriptional activation at target loci. We define a set of functional targets that drive aberrant oncogenic signaling programs in PRC1.1-mutated cells and primary patient samples. Activation of these PRC1.1 targets in BCOR-mutated cells confers acquired resistance to treatment while sensitizing to targeted kinase inhibition. Our study thus reveals a novel epigenetic mechanism that explains PRC1.1 tumor-suppressive activity and identifies a therapeutic strategy in PRC1.1-mutated cancer.Significance:We demonstrate that BCOR and BCORL1 mutations in leukemia unlink PRC1.1 repressive function from target genes, resulting in epigenetic reprogramming and activation of aberrant cell signaling programs that mediate treatment resistance. Our study provides mechanistic insights into the pathogenesis of PRC1.1-mutated leukemia that inform novel therapeutic approaches.This article is highlighted in the In This Issue feature, p. 85

Sequences of sgRNAs and primers

Supplementary Figure from BCOR and BCORL1 Mutations Drive Epigenetic Reprogramming and Oncogenic Signaling by Unlinking PRC1.1 from Target Genes

Clonal hematopoiesis (CH) is an aging-associated condition characterized by the clonal outgrowth of mutated preleukemic cells. Individuals with CH are at an increased risk of developing hematopoietic malignancies. Here, we describe a novel animal model carrying a recurrent TET2 missense mutation frequently found in patients with CH and leukemia. In a fashion similar to CH, animals show signs of disease late in life when they develop a wide range of myeloid neoplasms, including acute myeloid leukemia (AML). Using single-cell transcriptomic profiling of the bone marrow, we show that disease progression in aged animals correlates with an enhanced inflammatory response and the emergence of an aberrant inflammatory monocytic cell population. The gene signature characteristic of this inflammatory population is associated with poor prognosis in patients with AML. Our study illustrates an example of collaboration between a genetic lesion found in CH and inflammation, leading to transformation and the establishment of blood neoplasms.Significance:Progression from a preleukemic state to transformation, in the presence of TET2 mutations, is coupled with the emergence of inflammation and a novel population of inflammatory monocytes. Genes characteristic of this inflammatory population are associated with the worst prognosis in patients with AML. These studies connect inflammation to progression to leukemia.See related commentary by Pietras and DeGregori, p. 2234.This article is highlighted in the In This Issue feature, p. 2221

Menin interacts with oncogenic MLL1-fusion proteins, and small molecules that disrupt these associations are in clinical trials for leukemia treatment. By integrating chromatin-focused and genome-wide CRISPR screens with genetic, pharmacologic, and biochemical approaches, we discovered a conserved molecular switch between the MLL1–Menin and MLL3/4–UTX chromatin-modifying complexes that dictates response to Menin–MLL inhibitors. MLL1–Menin safeguards leukemia survival by impeding the binding of the MLL3/4–UTX complex at a subset of target gene promoters. Disrupting the Menin–MLL1 interaction triggers UTX-dependent transcriptional activation of a tumor-suppressive program that dictates therapeutic responses in murine and human leukemia. Therapeutic reactivation of this program using CDK4/6 inhibitors mitigates treatment resistance in leukemia cells that are insensitive to Menin inhibitors. These findings shed light on novel functions of evolutionarily conserved epigenetic mediators like MLL1–Menin and MLL3/4–UTX and are relevant to understand and target molecular pathways determining therapeutic responses in ongoing clinical trials.Significance:Menin–MLL inhibitors silence a canonical HOX- and MEIS1-dependent oncogenic gene expression program in leukemia. We discovered a parallel, noncanonical transcriptional program involving tumor suppressor genes that are repressed in Menin–MLL inhibitor–resistant leukemia cells but that can be reactivated upon combinatorial treatment with CDK4/6 inhibitors to augment therapy responses.This article is highlighted in the In This Issue feature, p. 1

RNA-Seq results

CRISPR screen results

Supplementary Data from BCOR and BCORL1 Mutations Drive Epigenetic Reprogramming and Oncogenic Signaling by Unlinking PRC1.1 from Target Genes

Supplementary Data from The Impact of Inflammation-Induced Tumor Plasticity during Myeloid Transformation

Response of BPDCN and AML cells to navitoclax and A-1331852. (A) MTT assay results for the indicated cell lines after 72 hours of exposure to the indicated doses of navitoclax (combined BCL-2/BCL-XL inhibitor). (B) MTT assay results for the indicated cell lines after 72 hours of exposure to the indicated doses of A-1331852 (BCL-XL only inhibitor). In both panels, data points represent mean of 3 replicates +/- SEM, line represents non-linear regression (curve fit).

PDF file 118K, This table includes genetic information of the AML patients studied in this manucript

PDF - 90KB, Legends for Supplemental Figures 1 through 6.

Adverse Events

Supplementary Table S2, provided as a separate Excel file. Contains a list of custom designed probes for expression profiling of prognostic long non-coding RNAs with the nCounter assay

PDF - 502KB, Supplementary figure 1. USP1 inhibitor SJB2-043 inhibits activity of native USP1 in a dose-dependent manner and causes a decrease in ID1, ID2 and ID3 levels in K562 cells. Supplementary figure 2. Knockdown of USP1 results in growth inhibition, increased apoptosis and cell cycle arrest in K562 cells. Supplementary figure 3. Analogs of USP1 inhibitor lead to ID1 destabilization in leukemic cells. Supplementary figure 4. Caspase inhibitor does not block the degradation of ID1 by USP1 inhibitors. Supplementary figure 5. Effects of USP1 inhibitors on growth of primary human cord blood CD34+ cells. Supplementary figure 6. USP1 inhibitors cause increase in Ub-FANCD2, Ub-PCNA, and p21, and decrease the HR activity.

Pathological analysis of human BPDCN growing as a patient-derived xenograft (PDX) in mice. Splenic tissue is shown stained with H&E (at 40x and 100x magnification), and human BCL-2, CD45, CD4, CD56, and CD123 (all at 40x) from animals bearing a representative BPDCN PDX.

Supplementary Figures and Tables

Supplementary Data, which contains text, tables and figures supportive of the results reported in the main manuscript. Text includes details about clinical trials protocols, RNA extraction techniques and statistical analyses. Tables include a list of prognostic long non-coding RNAs that are measured by the custom-designed nCounter assay and a list of mRNA transcripts that significantly associate with unfavorable lncRNA scores. Figures include scatterplots depicting the correlation of nCounter results in repeated measurements of samples of patients.

PDF - 86KB, Additional supplementary methods.

The transcription factor signal STAT5 is constitutively activated in a wide range of leukemias and lymphomas, and drives the expression of genes necessary for proliferation, survival, and self-renewal. Thus, targeting STAT5 is an appealing therapeutic strategy for hematologic malignancies. Given the importance of bromodomain-containing proteins in transcriptional regulation, we considered the hypothesis that a pharmacologic bromodomain inhibitor could inhibit STAT5-dependent gene expression. We found that the small-molecule bromodomain and extra-terminal (BET) bromodomain inhibitor JQ1 decreases STAT5-dependent (but not STAT3-dependent) transcription of both heterologous reporter genes and endogenous STAT5 target genes. JQ1 reduces STAT5 function in leukemia and lymphoma cells with constitutive STAT5 activation, or inducibly activated by cytokine stimulation. Among the BET bromodomain subfamily of proteins, it seems that BRD2 is the critical mediator for STAT5 activity. In experimental models of acute T-cell lymphoblastic leukemias, where activated STAT5 contributes to leukemia cell survival, Brd2 knockdown or JQ1 treatment shows strong synergy with tyrosine kinase inhibitors (TKI) in inducing apoptosis in leukemia cells. In contrast, mononuclear cells isolated form umbilical cord blood, which is enriched in normal hematopoietic precursor cells, were unaffected by these combinations. These findings indicate a unique functional association between BRD2 and STAT5, and suggest that combinations of JQ1 and TKIs may be an important rational strategy for treating leukemias and lymphomas driven by constitutive STAT5 activation. Mol Cancer Ther; 13(5); 1194–205. ©2014 AACR.